1. Field of the Invention
This invention relates to data communication equipment which serves a plurality of central processing units (CPUs) and which transfers data between these CPUs.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 3-501178, for example, describes data communication equipment which serves a plurality of central processing units in one control system, and transfers data between the CPUs. In the data communication equipment of this kind, data can be transferred mutually while the CPUs execute, in parallel, mutually different processes, and the data processing speed of the control system can be improved as a whole.
When such data communication equipment is applied to a trouble shooting apparatus for automobiles as described, for example, in Japanese Unexamined Patent Publication (Kokai) No. 64-55605, it may be possible to individually connect each CPU to a monitor device for trouble diagnosis by connecting each CPU to each of various sensors so as to detect any trouble. When a predetermined sensor is designated by the monitor device according to this arrangement, the CPU connected to this sensor can instantaneously read any trouble at this sensor.
In the data communication equipment of this kind, however, signal lines and input/output ports must be provided in data paths for transferring the data between the CPUs and for each direction of the data transfer. In the case of the trouble shooting apparatus described above, for example, the same number of input/output ports as the number of the CPUs must be provided to the monitor device, and each CPU and its input/output port must be individually connected by a pair of signal lines. For this reason, the circuit construction of the apparatus becomes unavoidably complicated.